The present invention relates generally to a laser beam target for use with an apparatus capable of emitting a reference laser beam of light along a predetermined path and, more particularly, to such a laser beam target which includes a plurality of projections on at least one surface thereof for directing at least a portion of the laser beam of light into a specific range of viewing angles away from the path.
Reference laser beam systems have been employed-in the past in numerous surveying and construction applications. In one such system, a laser beam projector provides a stationary laser beam which establishes a reference line of light. In use, the projector may, for example, be located in a construction site at a desired grade for laying sections of pipe. A laser beam target may be placed within each section of pipe being laid in order to assist the workers in determining the proper position for each section. By aligning the reference line of light with reference indicia on the target, each section can be properly positioned at the site.
In a further system, a laser beam projector provides a rotating laser beam which establishes a reference plane. In use, the projector may, for example, be mounted at or near the desired height of a hanging ceiling grid in a building under construction. The beam is rotated in a horizontal plane to provide a continuous, visible plane of light that creates a constant horizontal benchmark of elevation over the entire work area. A laser beam target may be mounted onto the ceiling grid in order to assist workers in determining the proper height for the ceiling throughout the room. The ceiling grid is leveled and mounted at the proper height by lining up reference indicia on the laser beam target with the rotating laser beam. Such a system has also been used for aligning drywall.
It is known in the prior art to provide a textured or ground surface on a laser beam target for diffusing an incoming beam of light symmetrically about the beam's axis to permit viewing of the beam striking the target from off-beam-axis positions. It is also known in the prior art to include glass fibers embedded within a laser beam target to diffuse an incoming beam of light symmetrically about the beam's axis to also permit viewing of the beam striking the target from off-beam-axis positions.
It is has been found that it is sometimes difficult to determine when a rotating beam or a reference line of light is in alignment with reference indicia located on one of the above-discussed prior art laser beam targets. Each prior art target diffuses an incoming beam of light into a broad range of viewing angles wherein the range is symmetrical about the beam's axis. As a result, the user receives only a very small fraction of the available beam power when viewing the target from a comfortably accessible off-beam-axis position, and thus sees a very dim image of the beam where it strikes the target. The remaining available beam power is wasted in unused directions. Thus, if a laser beam target is mounted in a pipe, a worker lining up the target with the reference line of light must position himself so that his line of sight is substantially in line with the path of travel of the reference light if he desires to increase the visibility of the reference beam of light on the target. This may result in the worker locating himself in an awkward position to line up the target with the reference line of light. Likewise, if a laser beam target is mounted on an overhead ceiling grid, a worker lining up the target with the laser beam must position himself so that his line of sight is substantially in the same plane as the rotating laser beam if he desires to increase the visibility of the reference beam of light on the target. This may also result in the worker having to position himself in an awkward position, e.g., on a supporting object, in order to line up the target with the laser beam.
Accordingly, a need exists for an improved laser beam target which is capable of directing a major portion of a reference beam of light emitted from a projector into a specific range of viewing angles away from its path of travel which includes positions easily accessible to the eyes of a worker viewing the target, thereby permitting a worker viewing the target to more easily determine when the reference beam of light is in alignment with appropriate indicia on the target.